I think I have the passages all mapped out correctly in the slew engine, and I made up a set of screen captures showing them from several angles. Was just about to post them, but it looks like PostImage's website has thrown a rod, and I cannot get in to upload the pictures. Fortunately their servers appear to still be serving out pics that were already uploaded.

Okay, PostImage is back fully alive again, here we go on the internal passages...

I have been 3D modeling up the slew and crowd engines (same design), based on the cross-section drawings in the patent from 1907 that Marion filed on it. Quite a complex little beast, with the forward/reverse and the throttle all controlled by one central valve, and it only has one eccentric/valve per cylinder, keeping it a very compact unit. The central valve switches the steam and exhaust back and forth between passages, as well as slowly allows more steam through as it is moved farther in each direction. It is a hollow spool valve with the incoming steam coming in the center, going out either end into the passages in the block. It rides inside a sleeve with patterns of holes that allow more steam past as the valve moves farther along.

Here is what the outside of the cylinder block looks like:and with some of the outer skins removed:To help me track the passages, I did a bunch of color coding. In the previous image, the red is the valve slider, and the green is the block containing the 5 (yes 5) passages, two to the ends of the cylinders, three to carry steam/exhaust around. On the top plate, exposed in that picture, the outer two rectangular ports in the center section always carry steam into the steam chests, to keep the valve sliders pressed onto the valve faces. The inner three ports swap between carrying steam and exhaust, depending where the slider is.In this next picture, there is more of the structure removed, better showing the valve sliders, and the sleeve (with all the holes) that the central control valve slides in showing.In the rest of the pictures, I inverted what you are seeing - I took a solid block inside the engine, and used the structure of the engine to cut away anyplace where a wall or part was, so what you are seeing now are the passages and ports, usually empty space, converted to solid.More color coding here. The purple at the front is one set of passages, the brown behind it is another, and the dark blue behind that is the third. The yellow and white are the passages under the steam chest that go to the cylinder ends. The lighter blue/purple arcs over the sides are the passages inside the valve slider, and the top of the purple under it, shaped like a semi-circle, is the area in the recess on the bottom of the valve slider, which normall would do all the work, but in this engine it only does half, the upper semicircle does the rest.Here is a view from the back corner:and a view from underneath:As you can see, the different colored passages wind around each other, but do not touch each other. Depending on where the central control valve is, the steam and exhaust will make thier way through the passages in the body of the engine, and the two passages inside the valve sliders will communicate to the yellow/white ports into the cylinders.

Quite a mechanism, isn't it!

These shapes are not something that I made up, they are how things are shaped in the actual engine, as close as I could come to duplicating the patent drawings into three dimensions. The large curves on the bottom of it all are where things wrap around the tops of the cylinders.

Now, for those of you that do casting, can you give me ANY clue as to how the heck they sand cast this sucker? I know that there are ways to insert pre-formed pieces of sand to make ports, but this many layers? Remember, this engine has 10" pistons, and the cylinders are about 14.4" long, so this whole thing is pretty big.

For the model, which will be somewhere in the neighborhood of 1:12 to 1:20 scale, doing ports that duplicate this exactly is impossible (at least for me, unless I can train some tiny elves to use teensy angle grinders to carve it from solid). I have, however, had some ideas on duplicating most of the functions of this using a simpler set of ports, and with spool valves on the cylinders as well as in the central section - just have that sketched on paper so far, need to convert it to a 3D model, then will share that in a future post. I think that in that form I can keep the same outer size of the engine, in a form that I can whittle out on the lathe/mill from a solid chunk. Maybe.

Whew. Been an intense several days working on this, I need chocolate chip cookies!!

Given that it's difficult to make a small engine run slowly, the gear ratios may need to change from the prototype in order to have the shovel move in a realistic manner.

Thats very possible, I did change the ones on the Lombard for that reason. On this one, the ratios are already fairly high, a lot is going to depend on what scale I end up at for the model. The gear boxes are big enough that changing the ratios a bit wont be noticeable in the model. For the initial plans, with everything done at full 1:1 scall to document the real machine, I am sticking with the actual tooth counts (at least as close as I can get, may be off a tooth or two on some of the ones hidden deep in the bowels).

Oh, and forgot to point out in the last picture - there are two pipes coming out the top of the engine, the upper one is the steam input pipe from the boiler, the one lower down closer to the centerline of the cylinders is the exhaust output pipe.

Hi Chris, amazing valve and port design. I don't know how you figured it out, let alone the original designers. I suppose it developed in stages.

Could you make them by cutting plates matching the vertical slices, stacking, pinning for alignment and silver soldering them all together?

MJM460

Making it from slices might work, at least down to a certain scale. Getting a seal all the way through on all those surfaces would be a big challenge though. I have worked out a version that just uses spool valves on all three positions that I think is practical for model sizes, need to loft it up in 3d to be sure it can be made. As usual with a spool valve model, there would be cross passages to drill, then have the end of the hole plugged. I will post that version once I get it drawn.

For drawing up the real engine, it was all taken from the patent images, which included 11 different outside and cross section views, very complete and incredibly well done. The genius behind it appears to be Charles B King, who had quite a range of inventions. His brother George and Harry Barnhart were the founders of Marion Steam Shovel.

Chris, Could it be 3d printed then investment cast? Looking forward to seeing completed parts.

Dave

Seems like that would work. From what I've seen on prices on Shapeways, it would be pretty expensive though. They do have restrictions on interior hollow spaces, since they need to be able to get the powders out when they print the form that they cast from. Could handle that with some plugs, I guess.

I would expect that the cores and molds were made up of multiple, but simpler parts, and then glued together during the final mold assembly. There were/are recipes for making baked sand cores using not much more than flour, water, molasses and sand. The cores for modern inlet manifold passages and other complex parts are made up of many small parts glued together in a jig. This assembly is then placed in the mold, which forms the outside of the part, and the part cast in metal.

I would expect that the cores and molds were made up of multiple, but simpler parts, and then glued together during the final mold assembly. There were/are recipes for making baked sand cores using not much more than flour, water, molasses and sand. The cores for modern inlet manifold passages and other complex parts are made up of many small parts glued together in a jig. This assembly is then placed in the mold, which forms the outside of the part, and the part cast in metal.

Well, I think the 3D model of the full-size slew/crowd engine is complete - got the valve eccentrics/rods, and piston/conrods, crankshaft all in. Here are some pictures of the engine and some cutaways:

Next on the list is a mock-up of the passages/valves for an attempt at a simpler version that will work at small model scale, but first a few days away from the computer to let the little grey cells recover from this one!!

EDIT: and could not resist seeing how it looks on the main boom. Still need to make the spur gears for either side, and get the engine placement tweaked so the gears mesh correctly, but looks pretty impressive up there!